Thursday, 21 January 2010

Do you have any problems relating to analytical chemistry for pharmaceuticals or training? Send your questions to the MTS helpdesk using our contact form.

Question:"Recently I have ordered a new analytical balance for my lab. I want to know what precautions I will have to take for proper installation. And as for calibration, up to what range of weights should I verify?”

Answer:“The instructions supplied with a new analytical balance are usually quite comprehensive and provide information on how to set up the balance correctly taking into account suitable location and internal calibration capabilities. Some other considerations (as provided by Scientech Balances) are as follows:

Set up the balance on a firm weighing table and even surface. Turn the adjustable feet until the balance is level using the spirit level/bubble indicator as guidance.

Avoid exposing the balance to vibrations during weighing. Corners of rooms are usually less prone to vibrations.

Best operating temperature is about 20°C/68°F at about 50% relative humidity. If you transfer the balance to a warmer area, make sure to condition the balance for about 2 hours at room temperature, leaving the unit unplugged from AC power. This is because the moisture in the air can condense on the surfaces of a cold balance whenever it is brought into a substantially warmer place. Never expose the balance to extreme moisture over long periods.

Protect the balance from drafts that come from open windows or doors. Heat and air-conditioning ducts will also product draft resulting in unstable readings.

Use caution when using weigh containers made of plastic since plastic is more prone to holding a electrostatic charge. If the samples being weighed hold static electricity an aftermarket static ionizer maybe needed for ionization for static removal. Static charges tend to develop when different materials rub against one another. Some materials can pick up excess electrons, resulting in negative static charges while other materials give up electrons, resulting in a positive charge. If the charged material is non-conducting (as are films, glass lenses and plastics), then the static charge remains.

Allow sufficient space around the balance for ease of operation and keep away from radiating heat sources.

Modern analytical balances typically include internal calibration features but regularly checking the accuracy against external calibrated masses is good practice. The calibration weights which you should verify will depend on the operating range of the balance so choose weights which bracket the range of weights which you will use the balance to measure and perhaps one or two spaced out throughout the range."